UC Riverside – HPCwirehttps://www.hpcwire.com
Since 1987 - Covering the Fastest Computers in the World and the People Who Run ThemFri, 09 Dec 2016 21:51:05 +0000en-UShourly1https://wordpress.org/?v=4.760365857New Hope for Graphene-based Logic Circuitshttps://www.hpcwire.com/2013/09/06/new_hope_for_graphene-based_logic_circuits/?utm_source=rss&utm_medium=rss&utm_campaign=new_hope_for_graphene-based_logic_circuits
https://www.hpcwire.com/2013/09/06/new_hope_for_graphene-based_logic_circuits/#respondFri, 06 Sep 2013 07:00:00 +0000http://www.hpcwire.com/2013/09/06/new_hope_for_graphene-based_logic_circuits/As an excellent conductor of heat and electricity, graphene is a promising electronics substrate, but it can't be switched on and off like silicon can. With no solution in sight, a team of UC Riverside researchers has taken a completely new approach.

]]>For more than a half century, computer processors have increased in power and shrunk in size at a phenomenal rate, but the exponential advances described by Moore’s law are winding down. Electronics based on silicon complementary metal–oxide–semiconductor (CMOS) technology are coming up against the physical limitations of nanoscale. Currently, there is no technology to take the place of CMOS, but a number of candidates are on the table, including graphene, a one-atom thick layer of graphite. Research suggests this incredibly strong and lightweight material could provide the foundation for a new generation of nanometer scale devices.

Scanning electron microscopy image of graphene device used in the study. The scale bar is one nanometer.

As an excellent conductor of heat and electricity, graphene is a promising electronics substrate, yet other characteristics of this material have stymied its progress as a silicon alternative. To address these limitations, researchers at the University of California Riverside have taken a completely new approach.

Semiconductor materials have an energy band gap, which separates electrons from holes and allows a transistor to be completely switched off. This on/off switch enables Boolean logic, the foundation of modern computing.

Graphene does not have an energy band gap, so a transistor implemented with graphene will be very fast but will experience high leakage currents and prohibitive power dissipation. So far, efforts to induce a band-gap in graphene have been unsuccessful, leaving scientists to question the feasibility of graphene-based computational circuits.

But Boolean logic is not the only way to process information. The UC Riverside team showed that it was possible to construct viable non-Boolean computational architectures with the gap-less graphene. Their solution relies on specific current-voltage characteristics of graphene, a manifestation of negative differential resistance. The researchers demonstrate that this intrinsic property of graphene appears not only in microscopic-size graphene devices but also at the nanometer-scale – a finding that could set the stage for the next generation of extremely small and low power circuits.

“Most researchers have tried to change graphene to make it more like conventional semiconductors for applications in logic circuits,” Alexander Balandin, a professor of Electrical Engineering, said. “This usually results in degradation of graphene properties. For example, attempts to induce an energy band gap commonly result in decreasing electron mobility while still not leading to sufficiently large band gap.”

“We decided to take alternative approach,” Balandin continued. “Instead of trying to change graphene, we changed the way the information is processed in the circuits.”

]]>https://www.hpcwire.com/2013/09/06/new_hope_for_graphene-based_logic_circuits/feed/03829The Week in Reviewhttps://www.hpcwire.com/2010/10/14/the_week_in_review/?utm_source=rss&utm_medium=rss&utm_campaign=the_week_in_review
https://www.hpcwire.com/2010/10/14/the_week_in_review/#respondThu, 14 Oct 2010 07:00:00 +0000http://www.hpcwire.com/?p=5075BLADE Network Technologies unveils a single-chip 40 Gigabit Ethernet switch capable of one terabit of throughput to the datacenter; and UC Riverside physicists make breakthroughs using graphene as a spin computing substrate. We recap those stories and more in our weekly wrapup.

Switch maker BLADE Network Technologies (BLADE) today unveiled the RackSwitch G8264, a single-chip 40 Gigabit Ethernet (GbE) top-of-rack switch. The switch delivers more than one terabit of low-latency throughput to the datacenter. This is the first time that a single-chip switch is available for terabit-scale deployment of 10GbE.

The new switch touts 64-10GbE ports, up to four-40GbE ports and 1.28 terabits of non-blocking throughput. Designed to handle I/O-intensive and highly virtualized workloads, the switch is well suited for HPC clusters, cloud computing, and algorithmic trading.

BLADE is aiming to fulfill the needs of mainstream enterprise datacenters, which are responding to increased data demands by increasingly deploying servers equipped with 10GbE. BLADE is going forward with the belief that 40GbE is the next logical step. Higher speed uplinks, such as 10/40 Gigabit Ethernet switches, will be required to handle the increased network bandwidth of the next-generation of datacenters.

According to Vikram Mehta, president and CEO, BLADE Network Technologies:

“BLADE is proud to break the terabit barrier in a single-chip design with the RackSwitch G8264. Our new switch is designed for today’s most demanding requirements at the datacenter edge to interconnect highly utilized servers equipped with 10 Gigabit Ethernet and provide seamless migration to 40 Gigabit upstream networks.”

The RackSwitch G8264 will be available in November at a cost of $22,500 USD. Interested parties can view the product at the upcoming Supercomputing Conference (SC10).2

UC Riverside Physicists Advance Spin Computing

“Spin computing” — aka “spintronics” offers great potential for the future of computing — think superfast computers that can overcome present Moore’s Law limitations while using less energy and generating less heat than the current batch of number crunchers.

Here’s how it works: electrons can be polarized so that they have a particular directional orientation, called spin. An electron can either be polarized so attain two states, called “spin up” or “spin down.” Storing data with spin would effectively double the amount of data a computer could store since it allows two pieces of data to be stored on an electron instead of just one, as is currently the case.

While researchers have been working on the technology for about four decades, it’s not quite ready for primetime. This week, however, Physicists at the University of California, Riverside have taken spintronics to the next level by successfully achieving “tunneling spin injection” into graphene. Their study results appear this week in Physical Review Letters.

Tunneling spin injection is a term used to describe conductivity through an insulator. Graphene, brought into the limelight by this year’s Nobel Prize in physics, is a single-atom-thick sheet of carbon atoms arrayed in a honeycomb pattern. Extremely strong and flexible, it is a good conductor of electricity and capable of resisting heat.

While graphene has characteristics that make it a very promising candidate for use in spin computers, the electrical spin injection from a ferromagnetic electrode into graphene is inefficient. Additionally, and even more troubling to the research team, observed spin lifetimes are thousands of times shorter than expected theoretically. Longer spin lifetimes are important because they allow for more computational operations.

The research team, led by Roland Kawakami, an associate professor of physics and astronomy, was able to dramatically increase the spin injection efficiency by inserting an insulating layer, known as a “tunnel barrier,” in between the electrode and the graphene layer. The team thus achieved the first demonstration of tunneling spin injection into graphene, and the 30-fold increase spin injection efficiency set a world record.

The Kawakami lab was also to reconcile the short spin lifetimes of electrons in graphene. They discovered that using the tunnel barrier increased the spin lifetime. According to Kawakami, graphene has the potential for extremely long spin lifetimes.

The next step for the Kawakami lab is to demonstrate a working spin logic device. Ultimately, a chip capable of manipulating the spin of a single electron could pave the way for futuristic quantum computers.